1.
override func viewDidLoad() { super.viewDidLoad() let rect = CGRect(x: 0.0, y: -70.0, width: view.bounds.width, height: 50.0) let emitter = CAEmitterLayer() emitter.frame = rect view.layer.addSublayer(emitter) emitter.emitterShape = CAEmitterLayerEmitterShape.rectangle //kCAEmitterLayerPoint //kCAEmitterLayerLine //kCAEmitterLayerRectangle emitter.emitterPosition = CGPoint(x: rect.width/2, y: rect.height/2) emitter.emitterSize = rect.size let emitterCell = CAEmitterCell() emitterCell.contents = UIImage(named: "appLogo")!.scaleImageToWidth(30).cgImage emitterCell.birthRate = 120 //每秒产生120个粒子 emitterCell.lifetime = 3 //存活1秒 emitterCell.lifetimeRange = 3.0 emitter.emitterCells = [emitterCell] //这里可以设置多种粒子 我们以一种为粒子 emitterCell.yAcceleration = 70.0 //给Y方向一个加速度 emitterCell.xAcceleration = 20.0 //x方向一个加速度 emitterCell.velocity = 20.0 //初始速度 emitterCell.emissionLongitude = CGFloat(-Double.pi) //向左 emitterCell.velocityRange = 200.0 //随机速度 -200+20 --- 200+20 emitterCell.emissionRange = CGFloat(Double.pi/2) //随机方向 -pi/2 --- pi/2 //emitterCell.color = UIColor(red: 0.9, green: 1.0, blue: 1.0, // alpha: 1.0).CGColor //指定颜色 emitterCell.redRange = 0.3 emitterCell.greenRange = 0.3 emitterCell.blueRange = 0.3 //三个随机颜色 emitterCell.scale = 0.8 emitterCell.scaleRange = 0.8 //0 - 1.6 emitterCell.scaleSpeed = -0.15 //逐渐变小 emitterCell.alphaRange = 0.75 //随机透明度 emitterCell.alphaSpeed = -0.15 //逐渐消失 }
2. UIimage拓展
extension UIImage { /// 将当前图片缩放到指定宽度 /// /// - parameter width: 指定宽度 /// /// - returns: UIImage,如果本身比指定的宽度小,直接返回 func scaleImageToWidth(_ width: CGFloat) -> UIImage { // 1. 判断宽度,如果小于指定宽度直接返回当前图像 if size.width < width { return self } // 2. 计算等比例缩放的高度 let height = width * size.height / size.width // 3. 图像的上下文 let s = CGSize(width: width, height: height) // 提示:一旦开启上下文,所有的绘图都在当前上下文中 UIGraphicsBeginImageContext(s) // 在制定区域中缩放绘制完整图像 draw(in: CGRect(origin: CGPoint.zero, size: s)) // 4. 获取绘制结果 let result = UIGraphicsGetImageFromCurrentImageContext() // 5. 关闭上下文 UIGraphicsEndImageContext() // 6. 返回结果 return result! } }